How can you "respect someone as a person" if you don't respect their beliefs?
Unless of course you think that a person's beliefs are random or predestined and they had no choice in them whatsoever.
It's not that hard, don't you have any friends who do stupid things you don't respect? For instance I have a couple of friends who cheated on their girlfriends, something I don't respect at all and certainly don't approve of, yet I can still be friends with them because there is more to them as people than that. Likewise people are more than their beliefs, just because someone believes something stupid doesn't make them a person you can't be friends with.
To be more concrete, I think it is kind of nuts to believe in a God/gods, yet I still have friends who are christians. Sometimes you meet people and befriend them without ever knowing their religious beliefs.
So while I don't necessarily respect some peoples beliefs I still have respect for them as people and so refrain from being derogatory about it.